The present invention relates in general to the collection of samples of fugitive dust.
Fugitive dust is an airborne contaminant that is common in rural areas where unsurfaced gravel and dirt are the predominant road surfaces and in urban areas close to heavy industry and truck traffic, thus generating higher population exposures and accompanying public health impacts. The health effects of fugitive dust range from aggravation of the respiratory system to systemic addition of trace elements in the blood through inhalation and ingestion. Studies have shown that lead (Pb) in dust is responsible for significant increases in blood-Pb levels of persons living in close proximity to Pb-dust sources such as mining, smelting, recycling, and other industrial activities (Murgueytio et al., 1998; Kerin and Lin, 2010; Johnson and Bretsch, 2002; Thornton et al., 1990; Needleman et al., 1990). Trace metals associated with fly ash and bottom ash released from power plants and incorporating onto road surfaces can also have a direct effect on human health (Zeneli et al., 2011). Contaminated unsurfaced roads can be a persistent and unavoidable health hazard for those living beside or regularly traveling these roads.
A thorough characterization of fugitive dust generated from road surfaces in areas that have been shown to have trace metal and other contamination from legacy industrial processes is largely unknown. The collection of samples for the chemical characterization of fugitive dust has been largely limited to point sources where swabs are obtained from homes, vehicles, roadside vegetation, deposits on soils, cascading impactors, or collected by installing open pans near unsurfaced roadways in potentially contaminated areas (Erel and Torrent, 2010; Duggan and Inskip, 1985; Kerin and Lin, 2010).
These methods do not support repeatability and representativeness (Que Hee et al., 1985). Point-collections limit data interpretation to a small area or require the investigator to make gross assumptions about the origin of the sample collected. Swabs from homes and dashboards of vehicles only represent those particular locations, and contaminated dust collected in these environments is difficult to track back to a road surface. Roadside vegetation only represents a single point along a roadway, and many samples would need to be collected to represent an 8- to 16-km reach. Pan collection is generally unattended and can be compromised by vandals or weather and roadside vegetation; several of these would need to be deployed to represent an entire road reach. Surface soils that are alleged to be “transported dust” do not provide defensible results because the sample can be a mixture from several sources. Impactors are focused on particle size delineation collecting size ranges that will be harmful when inhaled and do not take into consideration that particle ingestion of all suspended sizes is a much larger contributor to elevated blood-Pb levels (Steele et al., 1990; Biggins and Harrison, 1980; Barltrop and Meek, 1979). Also, these samplers use greases, oils, and other compounds that facilitate collection of samples for analysis. This has been recognized as a problem for representative chemical analysis (USEPA, 1983).
Furthermore, and most importantly, these methods neither produce the needed quantity of sample for rigorous geochemical characterization and reference that would include the need for several grams of material to perform X-ray diffraction, total and sequential extraction, particle size analysis, gravity separation, and repeat analysis, nor provide a spatially integrated characterization of the health hazard. Given the human health concern of fugitive dust, field methods need to be refined to provide a representative, repeatable, and sufficient quantity of sample to better characterize the chemical hazard of this exposure mechanism.